Platen and printer

Abstract

In the present invention, the platen bar is compositely formed of three materials. For a sole layer, a material is used which has high hardness and strength, and has a property that the repulsion against the impact of the print wires is large. For an elastic layer, a material is used which transmits less vibration to the platen base in the print operation and absorbs the impact when the wires of a printhead strike the sole layer. For platen bases, a material is used which has a very high hardness, a high molding precision, and less dimensional change due to temperature change or change with time. The elastic layer is exposed on the surface and a gap roller is positioned at the exposure location. With this, the occurrence of the dent by the gap roller can be prevented when the printing on a copy form is performed.

What is claimed is: 
     
       1. A platen for an impact printer, said platen having a planar surface for supporting a print medium and comprising at least three contact layers including a top, middle, and bottom layer, said layers providing a mass tuned to energetically absorb repeated impacts from a print head applied to the planar surface through the print medium, said medium being slidably movable across said planar surface; wherein said top layer being formed from an inelastic polymer matrix composite comprising at least a carbon fiber reinforced plastic or resin, said top layer including the planar surface and a surface adjacent to the planar surface, said adjacent surface being bent to form an angle with the planar surface so as to constitute a receiving surface for said medium as it moves toward and across said planar surface;   wherein said middle layer being formed from an elastic rubber; and   wherein said bottom layer being formed from an inelastic thermosetting resin.   
     
     
       2. The platen according to claim 1, wherein said planar surface of the top layer is formed from the polymer matrix composite exhibiting a low surface coefficient of sliding friction to the print medium. 
     
     
       3. A printing apparatus comprising a printing medium, platen backing and supporting said medium, a print head mechanism for impressing marks on the medium by impacting said platen through the medium, and an arrangement for slidably moving the medium over the platen; wherein said platen comprises a planar surface for supporting the print medium and comprising at least three contact layers including a top, middle, and bottom layer, said layers providing a mass tuned so as to energetically absorb repeated impacts from the print head;   wherein said top layer being formed from an inelastic polymer matrix composite comprising at least a carbon fiber reinforced plastic or resin, said top layer including the planar surface and a surface adjacent to the planar surface, said adjacent surface being bent to form an angle with the planar surface so as to constitute a receiving surface for said medium as it moves toward and across said planar surface;   wherein said middle layer being formed from an elastic rubber-like material; and   wherein said bottom layer being formed from an inelastic thermosetting resin.   
     
     
       4. The printing apparatus according to claim 3, wherein said elastic rubber-like material forming said middle layer is selected from a set consisting of natural rubber, urethane rubber, silicone rubber, and vinyl chloride. 
     
     
       5. The printing apparatus according to claim 3, wherein the shape of the planar surface of said platen is selected from a set consisting of a substantially flat surface and a substantially convex surface. 
     
     
       6. The printing apparatus according to claim 3, wherein said planar surface of the top layer formed from the polymer matrix composite exhibits a low surface coefficient of sliding friction to the print medium.